1. Field of the Invention
The subject system relates to railway maintenance equipment and particularly to upgrading existing railway track beds by introducing a subgrade stabilization fabric or geotextile material between the subgrade and ballast. There are many advantages to be gained by introducing such a material from providing a support membrane over a poor load bearing subgrade to assuring proper drainage. With the development of a variety of new geotextile materials which additionally provide a filtering function which not only syphons water away or allows it to pass partially through the material, but prevents fine particles from passing upwardly from the subgrade into the ballast thus contaminating it, such installations become more economically attractive.
2. Description of the Prior Art
The major problem presented in any attempt to introduce a separation fabric to the railway bed subgrade, is to economically accomplish such from the time of removing the ballast from under the railway track to the time or point of replacing the ballast. While particularly troublesome switch or crossing areas may justify manual placement of the fabric, installations of several hundred feet or more require some form of automation.
Early attempts to solve the problem of continuously introducing a separation material are shown in Austrian Pat. No. 307,476 which issued from Austrian patent application Ser. No. 8250/67 filed Sept. 8, 1967. In one embodiment, the material is introduced by spraying, pouring or injecting the material directly on the subgrade where it is allowed to harden to a plastic material. Such attempts usually employed a tar type material which does not possess the many desirable properties of the recently developed geotextile materials.
The other technique of introducing the separation material disclosed in the aforementioned Austrian patent is to locate a supply roll of the plastic foil, underneath the track, parallel to the ties along with a welder for joining adjoining adjacent individual strips. The apparent disadvantage of this device is that the space below the track will only accommodate small rolls of material requiring frequent roll changes and welds. If the track is locally lifted to accommodate a larger supply roll, danger of over stressing become obvious.